U.S. patent number 4,180,787 [Application Number 05/853,530] was granted by the patent office on 1979-12-25 for filter for very short electromagnetic waves.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Gerhard Pfitzenmaier.
United States Patent |
4,180,787 |
Pfitzenmaier |
December 25, 1979 |
Filter for very short electromagnetic waves
Abstract
A filter for very short electromagnetic waves is disclosed in
which a plurality of resonators are formed in a row with each
resonator containing two filter circuits. The resonators are
operated in a dual mode and the filter circuits are arranged in an
electrical sequential manner. First and last filter circuits in a
direction of the transmitted energy are provided with input and
output lines, respectively. At least one additional coupling is
provided between at least two filter circuits which do not directly
follow one another in electrical sequential fashion. At least one
of the resonators provides two filter circuits which are not
adjacent with respect to one another in electrical sequential
fashion and are coupled via an additional coupling.
Inventors: |
Pfitzenmaier; Gerhard (Munich,
DE) |
Assignee: |
Siemens Aktiengesellschaft
(Berlin & Munich, DE)
|
Family
ID: |
5994312 |
Appl.
No.: |
05/853,530 |
Filed: |
November 21, 1977 |
Foreign Application Priority Data
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Nov 30, 1976 [DE] |
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2654283 |
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Current U.S.
Class: |
333/212; 333/227;
333/230 |
Current CPC
Class: |
H01P
1/2082 (20130101) |
Current International
Class: |
H01P
1/208 (20060101); H01P 1/20 (20060101); H01P
007/06 (); H01P 001/20 (); H01P 001/16 () |
Field of
Search: |
;333/73W,73R,83R,83A,76,98R,7R,202,208,212,227,230 |
References Cited
[Referenced By]
U.S. Patent Documents
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3697898 |
October 1972 |
Blachier et al. |
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Foreign Patent Documents
Other References
Lin-"Journal of Applied Physics", vol. 22, No. 8, Aug. 1951; pp.
989-1001. .
Williams-"IEEE Transactions on Microwave Theory and Techniques",
vol. MTT-18, No. 12, Dec. 1970; pp. 1109-1113. .
Atia-"IEEE Transactions on Microwave Theory and Techniques", vol.
MTT-22, No. 4, Apr. 1974; pp. 425-431. .
Atia et al.-"Narrow-Bandpass Waveguide Filters", in IEEE Trans. on
Microwave Theory and Techniques, vol. MTT-20, No. 4, Apr. 1972; pp.
258-265. .
Rhodes et al.-In-Line Waveguide Selective Linear Phase Filters in
IEEE Trans. on Microwave Theory and Techniques, vol. MTT-22, No. 1,
Jan. 1974; pp. 1-5. .
Atia et al.-"Non-Minimum Phase, Optimum Amplitude, Bandpass
Waveguide Filters", Conference 1973, G-MTT International Microwave
Symposium, Digest of Technical Papers, Boulder, Colo., U.S.A., 4-6,
Jun. 1973; pp. 210-212..
|
Primary Examiner: Smith; Alfred E.
Assistant Examiner: Nussbaum; Marvin
Attorney, Agent or Firm: Hill, Van Santen, Steadman, Chiara
& Simpson
Claims
Iclaim as my invention:
1. A micro-wave filter comprising: a plurality of sequentially
connected filter circuits; a plurality of resonators, each
resonator operating as two of said filter circuits, said resonators
operating in a dual mode; individual resonators of said plurality
being arranged next to one another in a row; the filter circuits
all being coupled in a predetermined sequential mode of electrical
operation; first and last filter circuits being provided with
connection line means for input and output of micro-waves,
respectively; all sequentially adjacent resonators having coupling
means therebetween for coupling the micro-waves therebetween
without mode change; and at least one resonator providing two
filter circuits which are not directly adjacent in the sequential
mode of electrical operation and are coupled via an additional
coupling.
2. A filter as claimed in claim 1, in which the resonators, filter
circuits and couplings form a six-circuit Cauer band-pass filter,
the resonators being arranged in one row, and two resonators are
provided, each of which have two filter circuits which are not
adjacent in counting mode and are coupled via an additional
coupling.
3. A filter as claimed in claim 1, in which the resonators, filter
circuits, and couplings form an eight-circuit Cauer band-pass
filter, the resonators being arranged in one row, and three
resonators are provided each of which have two filter circuits
which are not adjacent in counting mode and are coupled via an
additional coupling.
4. A filter as claimed in claim 1 in which the resonators, filter
circuits, and couplings form a fourteen-circuit linear phase
filter, the resonators being arranged in one row and four
resonators are provided, each of which have two filter circuits
which are not adjacent in counting mode and are coupled via an
additional coupling.
5. The filter of claim 1 in which said additional coupling is a
coupling screw.
6. The filter of claim 1 in which three resonators are provided in
row form and two of the resonators each have one of said additional
couplings.
Description
BACKGROUND OF THE INVENTION
The invention relates to a filter for very short electromagnetic
waves, consisting of a plurality of resonators forming filter
circuits and which are coupled to one another, are operated in the
dual-mode, and whose first and last filter circuits in the
direction of the transmitted energy are provided with connection
lines for the supply and discharge of the electromagnetic energy.
An additional coupling is provided between at least two filter
circuits which do not directly follow one another in electrical
mode of operation and the individual resonators are arranged in the
form of rows next to one another.
Filters in micro-wave technology are, as is known, constructed from
a plurality of micro-wave resonators which are coupled to one
another, the coupling of which can take place either capacitively
or inductively. The resonators themselves can consist, for example,
of so-called coaxial line resonators or wave guide resonators.
In contrast to filters constructed with concentrated or lumped
circuit elements, as a result of the geometrically predetermined
configuration of the resonators it is not possible for every
circuit which can be constructed in the concentrated technique to
be readily transferred to the micro-wave frequency region. This
difficulty occurs, in particular, when it is necessary to produce
attenuation poles in the attenuation characteristic of the filter
and/or a transit time leveling in the pass band of the filter by
means of additional couplings of filter circuits. This difficulty
is eliminated by means of the arrangement, described in the German
OS 1 942 867, of resonators in adjacent rows with additional
over-couplings in the common partition wall of two resonators
arranged in different rows.
The possibility is also known of constructing micro-wave filters
with cavity resonators which are simultaneously operated in more
than one mode ("micro-wave filters employing a single cavity
excited in more than one mode", "Journal of Applied Physics", Vol.
22, No. 8, August 1951 by Wei-Guan Lin; "A Four Cavity Elliptic
Waveguide Filter", "IEEE Transactions on Microwave Theory and
Techniques", Vol. -MTT. 18, No. 12, December 1970 by Williams, A.
E.). Here preferably two identical but orthogonal loads are
employed in H.sub.101 - or H.sub.111 - resonators and are coupled
to one another by means of a coupling screw arranged at 45.degree.
to the direction of the E-vectors (dual mode). In this way two
electric oscillating circuits of a filter can be constructed in a
technically effective fashion in one single cavity resonator. On
account of the reduction in weight and volume of up to 50%, an
important field of application consists in satellite technology,
particularly since high electrical requirements are made on the
filters employed therein which become manifest in a relatively
large number of electric oscillating circuits.
As these filters also require attenuation poles and/or a leveling
of the transit time in the pass band, it is obviously desirable to
find suitable filter circuits in the dual mode technique for this
purpose. In this connection a proposed construction is known
("Nonminimum-Phase Optimum-Amplitude Band pass Waveguide Filters",
"IEEE Transactions on Microwave Theory and Techniques", Vol.
MTT-22, No. 4, April 1974 by Atia, A. E. and Williams, A. E.),
which, however, is restricted to filter circuits which are
symmetrical both with respect to structure and with respect to
element values. Furthermore they exhibit additional couplings which
frequently overlap, and cannot be preselected with respect to
number and geometric position within the filter arrangement. Also,
the number of electric oscillating circuits of the filter circuits
must amount to a multiple of 4 so that this proposal frequently
cannot be practically realized.
A possibility of improving the realizability of filter circuits
which are asymmetrical, particularly with respect to element values
and which can be operated in the dual mode has been disclosed by
the German OS 2 511 800 and consists in arranging the resonators in
adjacent rows and providing a different number of resonators in the
rows.
The coupling of filter circuits in spatially different resonators
is subject to the condition that the relevant two filter circuits
should be spatially orientated in like manner, so that e.g. their E
vectors run parallel with one another. This condition restricts the
number of theoretically conceivable couplings and thus the spectrum
of possible realizations or permits realizations only without the
use of additional couplings, which in themselves are desirable, or
only with production technology disadvantages.
SUMMARY OF THE INVENTION
An object of the invention is to overcome the above-mentioned
difficulties in a simple fashion, and, in particular, to provide
practical filter circuits with resonators operated in the dual mode
and additional couplings which, in the previously known
above-mentioned arrangements, either are not possible or are
possible only with considerable disadvantages.
According to the invention, a filter for very short electromagnetic
waves is provided consisting of a plurality of resonators with
filter circuits and which are coupled to one another, are operated
in the dual mode, and whose first and last filter circuits in the
direction of the transmitted energy are provided with connection
lines for the supply and discharge of the electromagnetic energy.
An additional coupling is provided between at least two filter
circuits which do not directly follow one another in the electrical
mode of operation and the individual resonators are arranged next
to one another in the form of rows. In accordance with the
invention, two filter circuits which are not adjacent in counting
mode and which are coupled via an additional coupling are provided
by means of at least one resonator.
The invention is based upon the recognition that in the previously
known arrangements, the source of the circuitry limitations is that
two filter circuits which are consecutive in counting mode are
always assigned to the same dual mode resonator.
A particular advantage of the invention is that the limitations
concerning the circuit structure which exist in the known prior art
are avoided so that consequently the number of filter circuits
which can be constructed in the dual mode is considerably
increased.
A production technology advantage in comparison to known filters is
that the filter structures which, in accordance with the prior art
must be constructed with two or more adjacent resonator rows, are
constructed in accordance with the invention in one row and the
individual resonators can thus be assembled in a simple manner by
means of flange connections.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a six circuit filter arrangement with two
additional over-couplings;
FIG. 2 illustrates a filter arrangement in accordance with the
invention for the realization of the circuit shown in FIG. 1;
FIG. 3 illustrates another six circuit filter arrangement with two
additional over-couplings;
FIG. 4 illustrates a further filter arrangement in accordance with
the invention for the realization of the circuit shown in FIG.
3;
FIG. 5 is a measured curve of the operating attenuation variation
of a filter arrangement constructed in accordance with the
invention;
FIG. 6 illustrates two equivalent circuits of an eight-circuit
filter arrangement with three additional over-couplings;
FIG. 7 illustrates a further filter arrangement in accordance with
the invention for the realization of the circuits shown in FIG.
6;
FIG. 8 illustrates a fourteen circuit filter circuit arrangement
with four additional over-couplings; and
FIG. 9 illustrates a filter arrangement in accordance with the
invention for the realization of the circuit shown in FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is an equivalent circuit of a six circuit Cauer bandpass
filter with concentrated or lumped circuit elements. This is a
four-pole circuit, in the shunt arms of which are arranged the
parallel oscillating circuits S1 to S6, and which are coupled via
the coupling inductances 1/2, 2/3, 3/4, 4/5 and 5/6 arranged in the
series arms. By way of additional coupling, a coupling inductance
1/6 is introduced between the parallel oscillating circuits S1 and
S6, and a coupling capacitance 2/5 is introduced between the
parallel oscillating circuits S2 and S5.
It has hitherto been impossible to construct a band-pass filter of
this kind by means of dual-mode resonators arranged next to one
another in a row, since, for example, in an experiment on a
construction employing H.sub.101 resonators, the E vectors of the
filter circuits S1, S6 and S2, S5 are arranged orthogonally to one
another and thus cannot be coupled via coupling slots in a
resonator wall.
For this reason previously only "pseudo-Cauer filters" of the n=6
order have been known, for example having been disclosed in the
article "Prototype characteristics of a class of dual-mode filters"
by R. D. Wanselow, published in IEEE Transactions on Microwave
Theory and Techniques of August 1975. These filters only possess
one attenuation pole above and below the pass band and thus are not
optimal.
In the exemplary embodiment illustrated in FIG. 2, a filter
arrangement in accordance with the invention is illustrated which
consists of three cavity resonators 1 to 3, and whose physical
equivalent circuit diagram is the circuit in FIG. 1. Here the
resonators are arranged in one row in such manner that resonators
arranged next to one another in each case possess a common
partition wall. The coupling elements which serve to couple the
resonators operated in the dual-mode are designed in known manner,
for example in accordance with the arrangement in FIG. 2 of German
Os 2 511 800, as slot openings and as shown in the instant case at
20 and 21 in FIG. 2.
The E vectors assigned to the individual modes are orthogonal
within a resonator and in FIG. 2 are provided with the references
E1 to E6 in accordance with the associated parallel oscillating
circuits S1 to S6 in FIG. 1. Each of the resonators is furthermore
provided with a coupling screw K16, K25 and K34 arranged at an
angle of 45.degree. between the E vectors corresponding to the
modes, in order to set the coupling between the orthogonal modes
operated therein. In the prior art, coupling screws of this kind
served merely to produce the coupling inductance between two
adjacent parallel oscillating circuits of the equivalent circuit
diagram, which thus followed one another in counting mode. In
accordance with the invention, the exemplary embodiment illustrated
in FIG. 2 contains at least one resonator, however, and in a
special situation the two resonators 1 and 2, which are assigned
the filter circuits S1, S5 and S2, S5, which do not follow one
another in counting mode, and therefore the coupling screws also
produce additional coupling reactances between non-adjacent filter
circuits.
In detail, in the exemplary embodiment, the resonator 1 is assigned
the filter circuits S1 and S6 and the corresponding E vectors E1
and E6, the coupling of which is effected via the coupling screw
K16 which has an inductive action. In this way the resonator 1
simultaneously contains the input-coupling terminal I and the
output-coupling terminal O of the filter. The resonator 2 which
adjoins the resonator 1 by a common partition wall is assigned the
filter circuits S2 and S5 and the corresponding, orthogonal E
vectors E2 and E5. The coupling of these filter circuits is
effected via the coupling screw K25 which is arranged to be offset
relative to the coupling screw K16 by a resonator edge, and thus
produces a capacitive coupling.
The coupling of resonator 1 to resonator 2, and of their assigned
modes with the corresponding, in each case parallel E vectors E1,
E2 and E6 is effected via coupling slots which are arranged in the
common partition wall of these resonators in each case at right
angles to the E vectors E1, E2 and at right angles to E6, E5, and
which are shown at 20 and 21 in FIG. 2.
The resonator 3 which adjoins the resonator 2 is assigned the
filter circuits S3 and S4, represented by the corresponding
orthogonal E vectors E3 and E4, the inductive coupling of which is
effected via the coupling screw K34. The coupling of resonator 2 to
resonator 3 is effected via further coupling slots which are
arranged in the common partition wall of these resonators at right
angles to the relevant E vectors E5, E4 and E2, E3 and which have
not been represented in the Figure.
In order to indicate the division of the oscillating circuits
between the individual resonators in the exemplary embodiment, the
circuit illustrated in FIG. 1 is provided with broken coordination
lines which run between two oscillating circuits constructed in a
resonator and are provided with the references assigned to the
relevant resonator.
An exemplary embodiment of the invention for a six-circuit Cauer
filter consists in a further equivalent circuit which is suitable
for construction in dual-mode technology and which is represented
in FIG. 3. This again is a four-pole circuit with parallel
oscillating circuits S1 to S6 in the shunt arms which are coupled
via coupling inductances 1/2 to 5/6. In place of the additional
coupling 2/5 in accordance with FIG. 1, however, a capacitive,
additional coupling 1/4 has been introduced which runs between the
oscillating circuits S1 and S4.
The individual oscillating circuits have again been divided between
the resonators in the exemplary embodiment in FIG. 4 in accordance
with the coordination lines of FIG. 3. In accordance with the
invention, the filter illustrated in FIG. 4 contains a resonator,
here the resonator 2, which is assigned the filter circuits S1 and
S4 which do not follow one another in counting mode and are
represented by the E vectors E1 and E4, whereas the resonator 1
contains the filter circuits S2 and S3 and the resonator 3 contains
the filter circuits S5 and S6.
In the resonator arrangement illustrated in FIG. 4, the electric
vectors E1 and E6 of the filter circuits S1 and S6 run parallel to
one another and can thus be magnetically coupled by means of a slot
in the partition wall of the resonators 2 and 3. The capacitive
additional coupling of the filter circuits S1 and S4 is achieved in
that the dual-mode coupling screw K14 of the resonator 2 is
displaced by 90.degree. relative to the like-orientated coupling
screws K23 and K65 of the resonators 1 and 3.
In comparison to the exemplary embodiment in FIG. 2, the
arrangement in FIG. 4 has the advantage that the input-coupling
terminal I and the output-coupling terminal O of the filter are not
contained in the same resonator, but in the resonators 2 and 3.
This largely avoids the occurrence of undesired additional
couplings.
FIG. 5 shows a measured curve of the operating attenuation
variation, which complies well with theory, of the exemplary
embodiment as shown in FIG. 4. This is a band-pass filter which has
been derived from the Cauer low-pass filter C6/26 dB/25 dB/B by
transformation, and is operated with H.sub.101 dual mode
resonators. (Theoretical data: middle frequency f.sub.o =4015 MHz,
pass band width .DELTA.fg=40 MHz, echo attenuation a.sub.e
.gtoreq.26 dB, blocking attenuation a.sub.b .gtoreq.25 dB). The two
clearly marked attenuation poles in each case beneath and above the
pass band can be gathered from the measured curve. For the echo
attenuation, values of a.sub.e .gtoreq.21 dB were measured in the
required pass band.
A realization with dual-mode resonators for the eight-circuit Cauer
band-pass filter with in each case three attenuation poles below
and above the pass band has not been previously known. The article
"Narrow Band-Pass Waveguide Filters" by A. E. Atia and A. E.
Williams in "IEEE Transactions on Microwave Theory and Techniques",
Vol. -MTT 20, No. 4, April 1972 only reports on a "Pseudo Cauer
Filter" of the n=8 order, with only in each case two attenuation
poles below and above the pass band.
FIG. 6 illustrates two equivalent circuits of the Cauer band-pass
filter of the n=8 order with concentrated elements. The second
circuit, provided with an inductive additional coupling K16, can be
constructed in accordance with the invention in the dual-mode
technique and is illustrated in the exemplary embodiment shown in
FIG. 7.
The filter in FIG. 7, which is constructed from the resonators 1 to
4 contains the two resonators 2 and 3, which accommodate the filter
circuits S2, S5 and S1, S6 which do not follow one another in
counting mode. The sign sequence for the additional couplings which
has been used in accordance with the associated equivalent circuit
diagram can be achieved with the locations shown in FIG. 7, of the
dual-mode coupling screws K34, K25, K16 and K78.
An advantageous application of the invention consists, for example,
also in the construction of a fourteen-circuit linear filter, of
which the equivalent circuit diagram is represented in FIG. 8, and
which contains two circuit sections in each case double-bridged for
transit time leveling in the pass band. The additional couplings
are entirely inductive and run between the circuits S1 and S6
(K16), S2 and S5 (K25), S9 and S14 (K914), and S10 and S13
(K1013).
As can be seen from the resonator arrangement in accordance with
the invention shown in FIG. 9 and having the equivalent circuit of
FIG. 8, the resonator arrangement consists of the resonators 1 to
7. Filter circuit pairs S1, S6; S2, S5; S9, S14; and S10, S13
comprise filter circuits which do not follow one another in
counting mode and are in each case combined in a resonator, the
resonators 3, 2, 5 and 6, respectively. An advantage with respect
to production technology in comparison to known arrangements of
this type consists in that the resonators are arranged in one
single row and thus can be easily assembled by means of flange
connections. An electrical advantage is achieved in particular by
the splitting of a 4 bridge circuit section into two double bridged
circuit sections as this results in dimensions for the coupling
slots which can be more easily achieved and simplifies the filter
tuning.
Although various minor modifications may be suggested by those
versed in the art, it should be understood that I wish to employ
within the scope of the patent granted hereon all such
modifications as reasonably and properly come within the scope of
my contribution to the art.
* * * * *